Photographic developer

ABSTRACT

A photographic developer containing sodium or potassium sulfite, carbonate and bromide, hydroquinone, 1-phenyl-3-pyrazolidone, and benzotriazole in aqueous solution yields heretofore unattained photographic efficiency when applied to plates and films in general use for scientific photography.

United States Patent Inventors John A. Difley Monrovia; William C. Miller, Pasadena, both of Calif. App]. No. 849,315 Filed Aug. 12, 1969 Patented Oct. 26, 1971 Assignee Carnegie Institution of Washington Washington, D.C.

PHOTOGRAPHIC DEVELOPER 2 Claims, 3 Drawing Figs.

US. Cl. 96/66,

. 96/663 Int. Cl G03c 5/30 Field of Search ..96/66, 66.1, 66.3, 66.2

[56] References Cited UNITED STATES PATENTS 3,005,7l0 10/1961 Levy 96/66 Primary Examiner-Norman G Torchin Assistant Examiner-Mary F. Kelley Attorney-Stowe" & Stowell ABSTRACT: A photographic developer containing sodium or potassium sulfite, carbonate and bromide, hydroquinone, lphenyl-3-pyrazolidone, and benzotriazole in aqueous solution yields heretofore unattained photographic efficiency when applied to plates and films in general use for scientific photography.

RELATIVE DEVELOPER EXHAUSTION PER LlTER SPECULAR DENSITY E 32 64 I28 RELATIVE EXPOSURE PATENTEDUET 25 IeII 3.61552 3 sIIEEI 10F a RELATIVE DEVELOPER EXHAUSTION PER LITER 35 I I I l I I I I L 3.0 0-76 (l5 MIN.) 2.5

g0- FRESH DEVELOPER o l l I l l l l 5.5 I I I I I I 3 O I I I I I I 9,; 3 5 I I I I I I I 30 MWP-Z (9 MIN.)

FRESH '5 DEVELOPER AFTER 1.0 685 80. IN. 5

Q I I 4 l I l I RELATIVE EX POSURE INVENTORS.

JOHN A. DIFLEY WILLIAM c. MILLER ATTORNEY- 1 PATENTEDnm 2s I97I ,515,523

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I I I a 3 S 9 2 MISNEIG INVENTORS. JOHN A. DIFLEY WILLIAM-"C. MILLER FIG. 2

ATTORNEYS.

PATENTEDUCT 26 Ian SHEET 3 OF 3 $386 M2251 9 w v ml z @355 20535992 ws'wao INVENTOR S. JOHN A. DI FLEY m QI ATTORNEY! PHOTOGRAPHIC DEVELOPER This invention relates to a photographic developer which produces the maximum developable image silver for a given exposure on types of photographic emulsions employed in scientific photography.

Photography is indispensable in many phases of astronomical and physical research because the photographic image is capable of recording anywhere from several tens of thousands to many millions of bits" of information in each square inch of negative material. Such records can be preserved for study generations of scientists. Often the older such records become the more valuable they are because they contain information about the condition of things at the time the photograph was made, such as the brightness and position of astronomical objects. Such records usually cannot be replaced at a future date because of changes with time in the conditions of the physical world.

The time required for many photographic exposures is long and extremely costly, and it is imperative that each one shall make the best possible use of the time available. For example, constant effort on the part of astronomers to reach farther and farther into space has resulted in the construction of ever larger telescopes at a cost of millions of dollars apiece. The operation of such huge instruments costs many hundreds, often thousands of dollars each night. The demands by as tronomers for observing time on these large instruments is so great that every means must be exploited to facilitate their work and provide the most efficient methods for achieving their objectives.

Manufactures of photographic materials have spent, and continue to spend, large sums in efforts to improve the speed or efficiency of their products and have achieved wonders over the past 30 years. Research scientists themselves have made significant improvements in the efficiency of photographic materials by devising special treatments applied just prior to, or during, exposure in the instruments. However, insufficient attention has been paid to one other phase of scientific photography-the efiiciency with which the exposed emulsion is developed into a visible, measurable silver image. Efficiency of development can be measured in terms of the amount of silver that is chemically reduced from the exposed silver halide in the emulsion by the action of the developer solution, for a given amount of exposure of the image.

It has long been known that certain developer formulations work better with some types of photographic emulsions than others. There is a large number of standard formulas published in the literature. Many tests have been made with these on various classes of photographic materials to find favorable combinations that produce specific desirable results. Such favorable combinations are usually recommended by the manufacturers of photographic materials for use with certain of their products. Astronomers have heretofore followed such recommendations.

We have now discovered a photographic developer composition particularly adapted to the requirements of scientific photography and the types of negative materials used therein, that maintains important negative characteristics no worse, and usually better, than those produced by currently recommended developers. Such characteristics include: (a) photographic efficiency (speed), (b) granularity of the image, (c) fringe and border effects, (d) gamma, (e) chemical fog, (f) development time, (g) developer keeping quality, (h)

illustrated in FIGS. 1, 2, and 3 of the drawings. It was found that a good average value of these characteristics could be met with a basic developer composition. Specific characteristics could be optimized still further by variations in the relative 5 quantities of the ingredients and/or substitution of another positive ion in certain of the salts comprising the formulation, such as substitution of potassium ion for sodium. The formula can also be adapted to specific types of photograph emulsion by similar variations for the purpose of optimizing the overall efficiency of that particular material.

It will be appreciated that the relative proportions and ranges of concentration of ingredients utilized will have to be modified to compensate for changes in the particular metal ion employed. Typical changes in concentration and range required by such substitutions are shown below:

Grams per Sulfite: I liter of solution Sodium 90-120 Potassium 50-70 Hydr0 quinone 8-12 l-phenyl-la-pyrazolidone 90 Benzotriazole 45-1. 0 Potassium bromide 1. 2-2. 8 Carbonate:

25 Sodium 40-70 Potassium 22-36 Potassium bromide Potassium carbonate 105 grams per liter of solution 10 grams per liter of solution 0.4 grams per liter of solution 0.6 grams per liter of solution 2.0 grams per liter of solution 30grams per liter of solution To assure maximum shelf life of the mixture it will be appreciated that the ingredients can be packaged separately or in combination in dry or liquid form, depending upon the characteristics of the substituted salts required for specific purposes.

With the above-mentioned photographic emulsions the development time is typically 7 minutes at 68 F., although this can be varied up or down to suit specific requirements, such as control of chemical fog, granularity, density range, informational sensitivity, and similar parameters.

The relative efficiency of any emulsion-developer combination can be expressed as the relative intensity of light, in arbitrary or absolute units, applied for a constant time through a suitable test instrument, required to produce a developed density (typically 1.0 above fog) at a specified wavelength for each type of emulsion sensitizing. For any given sample these data are conveniently presented in the following manner:

Relative Exposure/Chemical Fog Density 30.5 0.23 Table I gives such comparative data for several research emulsions commonly used in astronomy, each developed for the recommended time in the solution recommended by the manufacturer of the photographic material, and for our fordeveloper working life, etc. Several of these improvements are mulation, MWP-Z, specifically tailored to these emulsions.

TABLE I.RELATIVE EXPOSURE AND FOG Emulsion type Table (:o| 1 lin 1c:d

Emulsion type Ila-D Ila-E lla-F Ila- Measured at A 6,000 A. 6,450 A. 6,000 A. 4,600 A Measured at D 1.0 r Fog 1.0 r Fog 1.o r Fog 1.0 r Fog D-76 30. 5 .23 120. .21 101. 33 A. 15.0 21.3 .12 96.5 .22 74.5 .32 12.7 .17

From these comparative data it will be seen that the listed GRAD E T emulsions developed in the new solution consistently yield greater efficiency than in the best of other formulations.

Other important characteristics of photographic negative materials used for scientific purposesthat are affected by developing solutions are evaluated below GRANULARITY Microphotometer tracings of the granularity (output noise) of typical emulsions in the manufacturer's recommended developer and in MWP-Z were made. The new developer in no case gives greater granularityusually slightly lessat a given density than in the older formulation despite the increase in speed.

BORDER AND FRINGE EFFECTS Artificial fluctuations in density that occur with many developers at the edges of heavily exposed images are highly detrimental to most scientific photography. Comparative microphotometer tracings across image edges developed in the manufacturer's recommended solution and in MWP-2 were made. These tracings clearly showed the improvement obtained with the new formulation.

DEVELOPING CAPACITY The gradient, or slope of the characteristic (Hurter and Drifield) curve for negative materials is of the utmost significance in scientific photography when negatives are used for the determination of relative brightness of objects recorded on the negative. Frequently several different negatives must be compared with a single calibration standard when making such determinations. Any differences in gradient from plate to plate resulting from slight differences in the length of development can lead to serious errors. Such differences often occur as a result of human error in manipulating negatives through the solutions in the completely dark processing room. One of the very significant advantages of the new developer is its highly stable gradient, maintained over a wide range of development times, providing a degree of accuracy of derived results not available from negatives processed in other developers.

FIGS. 2 and 3 shows comparative results with MWP-2 and manufacturers recommended fonnulations for constant exposure samples developed for difi'erent lengths of time. Gradient versus development time is seen to be much more consistent with the new formation than with any of the standard solution.

What we claim is:

1. A photographic developer containing w-l20 gram s of sodium sulfite or 50-70 grams of potassium sulfite, 8-12 grams of hydroquinone, 0.25-0.90 gram of l-phenyl3- pyrazolidone, 0.46-1 .0 grams of benzotriazole, 1.2-2.8 grams of potassium bromide, and 22-36 grams of potassium carbonate of 40-70 grams of sodium carbonate in 1 liter of solution.

2. A photographic developer according to claim 1 containing grams of sodium sulfite, 10 grams of hydroquinone, 0.40 gram of l-phenyl-3-pyrazolidone, 0.6 gram of benzotriazole, 2 grams of potassium bromide, and 30 grams of potassium carbonate per liter of solution.

3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3615523 Dated Q t h Zfi 92] JOHN A. DI FLEY WILLIAM C MILLER It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In column 4, that portion of line 35 reading "Tr-120 grams" should read --90-120 grams--.

In column 4 that portion of line 40 reading "of 40-70 grams" should read --or 40-70 grams--.

Signed and sealed this 21 at day of March 1972.

; (SEAL) i Attest:

i EDWARD M.FLETCHER, JR. ROBERT GOTTSCHALK i Attesting Officer Commissioner of Patents i 

2. A photographic developer according to claim 1 containing 105 grams of sodium sulfite, 10 grams of hydroquinone, 0.40 gram of 1-phenyl-3-pyrazolidone, 0.6 gram of benzotriazole, 2 grams of potassium bromide, and 30 grams of potassium carbonate per liter of solution. 